Devices driven by batteries, such as portable information terminals typified by digital cameras, mobile telephones and PDAs (Personal Digital Assistants), have become widespread in recent years. In order to extend the time over which operation is possible using batteries, it is required that these devices consume little power.
Further, nowadays there are many occasions for automatic ticket processing using a commutation ticket constituted by an IC card or like, and admissions processing using an ID card. A wireless system that has been proposed for such occasions implements communication between the card and a gate by NFC (Near Field Communication), which is a contactless short-distance wireless scheme. In general, the distance over which an RF field (a radio-frequency electromagnetic field) is capable of being formed by short-distance radio that relies upon contactless electromagnetic coupling is on the order of tens of centimeters, and the communication speed is on the order of several hundred kilobytes per second.
Meanwhile, wireless LANs compliant with IEEE 802.11 are becoming increasingly popular for use in sending and receiving high-speed data, and novel technology such as UWB (Ultra-Wide Band) is being developed for wireless LANS of even higher speeds. In general, the communication distance of these wireless LANs is on the order of tens of meters to 100 m.
Further, an apparatus equipped for communication using a plurality of different wireless communication has been proposed in Prior Art Document 1 (the specification of Japanese Patent Application Laid-Open No. 2002-366988), by way of example. This document describes a method in which first and second communication means are provided and an emission of high-frequency power from the first communication means is halted when the second communication means has started data communication. This document also describes the provision of third communication means the transmission power of which is less than that of the first communication means, with the first and third communication means being switched between when the second communication means has started data communication. A public wireless communication scheme such as PDC (Personal Digital Cellular) or W-CDMA (Wideband-Code Division Multiple Access) is presumed as the first communication means. A wireless communication scheme that uses low-output radio waves or means other than radio waves, such as a contactless IC card, Bluetooth or IrDA (Infrared Data Association), is presumed as the second and third communication means.
In the example cited above, however, halting of or changeover from the first communication means is executed when the second communication means has started data communication. Consequently, in a case where a wireless LAN compliant with IEEE 802.11 is used as the first communication means, halting of the wireless LAN or changeover of the LAN to a wireless LAN of a different scheme is executed and the power of the first communication means cannot be controlled.
Generally, in a wireless LAN compliant with IEEE 802.11, the transmission power is fixed in conformity with the maximum conceivable communication distance. This means that is difficult to lower transmission power and reduce power consumption in cases where the communication distance is short and, hence, a low transmission power adequate. Unless battery capacity is enlarged, therefore, it is difficult to achieve long-term use.